The objective of this research program is to investigate the anatomy of the limbic system in the rhesus monkey. The rationale is that the phylogenetically ancient structures of the telencephalic limbic system are not static but have undergone a progressive development in concert with the expanding neocortex in primate phylogeny. On earlier reports have shown that this progression has manifested itself in unique connnections with the neocortex, offering the primate limbic system potential modes for participation in "higher cortical functions" often thought to be the exclusive province of the neocortex. The need to investigate such questions in a non-human primate is indicated by the fact that such connections are unique to the primate limbic system. We propose to continue thes research program by investigating: 1. the architectonics, connections and neuronal morphology of the uncal hippocampus; 2. the laminar termination of hippocampal afferents; 3. the cortical and intrinsic efferent connections of the amygdala; and 4. the efferent connections of the basal forebrain. These investigations will use standard histochemical stains and Golgi impregnation procedures to investigate architectonics and neuronal morphology. Connections will be studied using 3H-labeled amino acids and autoradiographic procedures to trace anterograde connections and both horseradish peroxidase and fluorescent dyes to retrogradely label the neuron of origin.